Optoelectronic device with increased open-circuit voltage

ABSTRACT

An optoelectronic device includes a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type different from the first conductivity type, and a photoelectric conversion region between the first semiconductor region and the second semiconductor region. The photoelectric conversion region is of a third conductivity type the same as the first conductivity type.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. provisional application No.62/809,712, filed Feb. 24, 2019 and priority from U.S. provisionalapplication No. 62/844,746, filed May 8, 2019, which are incorporated byreference herein in their entireties.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to an optoelectronic device, andmore particularly to a photovoltaic cell for converting optical signalinto electricity.

2. Description of the Prior Art

A photovoltaic (PV) cell, which is a device for converting radiation toelectrical energy, may comprise P-type and N-type diffusion regions.Radiation impinging on the photovoltaic cell creates electrons and holesthat migrate to the diffusion regions, thereby creating voltagedifferentials between the diffusion regions. The diffusion regions areelectrically connected to corresponding terminals to allow an externalelectrical circuit to be connected to and be powered by the photovoltaiccell. A passive photovoltaic cell is designed to convert radiation allthe way from UV to visible to IR ranges from sun, imposes specificrequirements on designing solar cells.

An active photovoltaic cell is designed to charge an electronicdevice/storage with light-emitting diodes (LEDs) or laser power. In anactive photovoltaic cell, the demand of converting single-wavelength ornarrow-band radiation spectrum from LEDs or laser may impose differentrequirements on designing cells, such as light from led/laser should beinvisible and eye-safe or the photovoltaic cell should bepower-efficient, i.e., large open-circuit voltage (V_(OC)) and largeshort-circuit current (I_(SC)).

SUMMARY OF THE INVENTION

It is one object of the present application to provide an improvedoptoelectronic device with increased open-circuit voltage.

One aspect of the present application provides an optoelectronic deviceincluding an optoelectronic unit including a photoelectric conversionlayer for converting an optical signal into an electrical signal; and afirst semiconductor layer and a second semiconductor layer sandwichingthe photoelectric conversion layer. The first semiconductor layer andthe second semiconductor layer have different atomic arrangements.

According to one embodiment, an optoelectronic device includes anoptoelectronic unit including a photoelectric conversion layer forconverting an optical signal into an electrical signal; and a firstsemiconductor layer and a second semiconductor layer sandwiching thephotoelectric conversion layer. The photoelectric conversion layerincludes a material including a Group IV element, the firstsemiconductor layer includes a material including a Group IV element,and the Group IV element of the first semiconductor layer is differentfrom the Group IV element of the photoelectric conversion layer.

According to one embodiment, an optoelectronic device includes anoptoelectronic unit including a photoelectric conversion layer forconverting an optical signal into an electrical signal. Thephotoelectric conversion layer includes germanium.

Another aspect of the present application provides an optoelectronicdevice including a first semiconductor region of a first conductivitytype; a second semiconductor region of a second conductivity typedifferent from the first conductivity type; and a photoelectricconversion region between the first semiconductor region and the secondsemiconductor region. The photoelectric conversion region is of a thirdconductivity type the same as the first conductivity type.

According to one embodiment, an optoelectronic device includes aphotoelectric conversion region including a first side and a second sideopposite to the first side; a first semiconductor region of a firstconductivity type; and a second semiconductor region of a secondconductivity type different from the first conductivity type. The firstsemiconductor region and the second semiconductor region are both overthe first side of photoelectric conversion region, and wherein thephotoelectric conversion region is of a third conductivity type the sameas the first conductivity type.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings:

FIG. 1 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with one embodiment of the presentapplication;

FIG. 2 is an enlarged view of an optoelectronic unit with asymmetricdouble intrinsic heterojunction configuration in accordance with oneembodiment of the present application;

FIG. 3 is a band diagram showing the band structure of theoptoelectronic unit in FIG. 2;

FIG. 4 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with another embodiment of thepresent application;

FIG. 5A is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 5B is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application.

FIG. 6 is a band diagram showing the band structure of the exemplaryoptoelectronic device of FIG. 5A;

FIG. 7 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 8 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 9 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 10 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 11 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 12 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 13 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 14A is a schematic, top-view diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 14B is a schematic, cross-sectional diagram along an A-A′ line inFIG. 14A;

FIG. 15 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 16 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 17 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 18 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device in accordance with still another embodiment of thepresent application;

FIG. 19 demonstrates simulation results of I-V curves of optoelectronicdevices in FIG. 11 with different peak concentrations; and

FIG. 20 shows the I-V curves of different optoelectronic devices.

DETAILED DESCRIPTION

In the following detailed description of the disclosure, reference ismade to the accompanying drawings, which form a part hereof, and inwhich is shown, by way of illustration, specific embodiments in whichthe invention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention.

Other embodiments may be utilized and structural, logical, andelectrical changes may be made without departing from the scope of thepresent invention. Therefore, the following detailed description is notto be considered as limiting, but the embodiments included herein aredefined by the scope of the accompanying claims.

In the present application, the term “germanium-silicon (GeSi)” refersto a Ge_(x)Si_(1-x), wherein 0<x<1. The term “intrinsic” refers to asemiconductor material without intentionally adding dopants.

As used herein, the terms such as “first”, “second” and “third” describevarious elements, components, regions, layers and/or sections, theseelements, components, regions, layers and/or sections should not belimited by these terms. These terms may be only used to distinguish oneelement, component, region, layer or section from another. The termssuch as “first”, “second”, and “third” when used herein do not imply asequence or order unless clearly indicated by the context.

Germanium (Ge) has high carrier mobility (e.g., high hole and electronmobility) and optical absorption as compared to silicon (Si). This isone reason why Ge is useful for devices that require enhancedperformance and/or high quantum efficiency. Ge grown on Si substrate maybe a suitable platform for active photovoltaic cells, e.g., it canabsorb NIR wavelengths >1.4 um that are invisible and eye-safe, withlarge quantum efficiency boosting I_(SC). However, when being processedas a photodiode, its relatively large dark current at a reverse-biassuggests the presence of defects as recombination centers at aforward-bias, which may reduce V_(OC) and the power efficiency.

Please refer to FIG. 1 and FIG. 2. FIG. 1 is a schematic,cross-sectional diagram showing an exemplary optoelectronic device 1 inaccordance with one embodiment of the present application. FIG. 2 is anenlarged view of an optoelectronic unit with asymmetric double intrinsicheterojunction configuration in accordance with one embodiment of thepresent application. As shown in FIG. 1, the optoelectronic device 1includes a substrate 10, an optoelectronic unit 20 supported by thesubstrate 10, and an optical element E disposed on the optoelectronicunit 20. According to one embodiment of the present application, forexample, the substrate 10 may include silicon. According to oneembodiment of the present application, for example, the optical elementE may include a spacer layer 30 disposed on the optoelectronic unit 20and the silicon substrate 10, and a lens 40 disposed on the spacer layer30.

According to one embodiment of the present application, the lens 40 isdisposed to focus incident light 500 toward the optoelectronic unit 20.According to one embodiment of the present application, the spacer layer30 may include optical transmissive material, which is transparent tothe target wavelength of the incident light 500. The opticaltransmissive material includes, but is not limited to, polymer,dielectric material, transparent material, partially transparentmaterial, or the like. The material may include, and is not limited to,Si, SiO₂, Si₃N₄, or any combination thereof. According to one embodimentof the present application, the spacer layer 30 may include a dielectricmaterial layer that is transparent to the incident light 500 such asnear IR (e.g., wavelength >750 nm), such that the incident light 500 canbe absorbed by the optoelectronic unit 20. Although not shown in thefigures, it is to be understood that the optoelectronic device 1 mayinclude multiple optoelectronic units 20, and the multipleoptoelectronic units 20 may be arranged in a two-dimensional array.

According to one embodiment of the present application, a material ofthe spacer layer 30 is different from a material of the lens 40.According to one embodiment of the present application, a thickness ofthe spacer layer 30 is greater than a thickness of the lens 40. Thespacer layer 30 is to enhance the amount of the incident light 500entering the optoelectronic unit 20. According to one embodiment of thepresent application, the spacer layer has a thickness not less than 5μm. According to one embodiment of the present application, thethickness of the spacer layer 30 is not more than 100 μm. According toone embodiment of the present application, a width w₁ of theoptoelectronic unit 20 is less than a width w₂ of the substrate 10.

According to one embodiment of the present application, theoptoelectronic unit 20 may be partially embedded in the substrate 10.According to another embodiment of the present application, theoptoelectronic unit 20 may be fully embedded in the substrate 10.According to still another embodiment of the present application, theoptoelectronic unit 20 may not be embedded in the substrate 10 and maybe entirely on the substrate 10.

As shown in FIG. 2, the optoelectronic unit 20 includes an asymmetricdouble intrinsic heterojunction configuration. According to oneembodiment of the present application, for example, the optoelectronicunit 20 includes a photoelectric conversion layer 201 for converting anoptical signal into an electrical signal, a first semiconductor layer210 disposed on a first side 201 a of the photoelectric conversion layer201, and a second semiconductor layer 220 disposed on a second side 201b of the photoelectric conversion layer 201. The photoelectricconversion layer 201 is sandwiched between the first semiconductor layer210 and the second semiconductor layer 220. The first semiconductorlayer 210 has a band gap greater than a band gap of the photoelectricconversion layer 201. According to one embodiment of the presentapplication, the second semiconductor layer 220 also has a band gapgreater than the band gap of the photoelectric conversion layer 201. Thefirst semiconductor layer 210 and the second semiconductor layer 220each with a band gap greater than the band gap of the photoelectricconversion layer 201 are for increasing the open-circuit voltage of theoptoelectronic unit 20. According to one embodiment of the presentapplication, the material of the substrate 10 is different from thematerial of the photoelectric conversion layer 201.

According to one embodiment of the present application, thephotoelectric conversion layer 201 has a thickness not less than 500 nm,not more than 10 μm, for higher efficiency. According to one embodimentof the present application, the first semiconductor layer 210 has athickness not less than 10 nm, not more than 1 μm, for better surfacepassivation of the photoelectric conversion layer 201. According to oneembodiment of the present application, the second semiconductor layer220 has a thickness not less than 10 nm, not more than 10 μm, for bettergrowth quality of the photoelectric conversion layer 201. According toone embodiment of the present application, the first semiconductor layer210 has an atomic arrangement that is different from that of the secondsemiconductor layer 220. For example, the first semiconductor layer 210is amorphous, and the second semiconductor layer 220 is crystalline. Theterm “crystalline” includes single crystalline or polycrystalline.According to one embodiment of the present application, the atomicarrangement can be determined by any suitable method, such as an X-raydiffraction analysis (XRD). According to one embodiment of theinvention, the first semiconductor layer 210 and the secondsemiconductor layer 220 are both intrinsic. According to one embodimentof the present application, the first semiconductor layer 210 is indirect contact with the photoelectric conversion layer 201. According toone embodiment of the present application, the second semiconductorlayer 220 is in direct contact with the photoelectric conversion layer201.

According to one embodiment of the present application, a material ofthe photoelectric conversion layer 201 is different from a material ofthe first semiconductor layer 210. According to one embodiment of thepresent application, a material of the photoelectric conversion layer201 is different from both a material of the first semiconductor layer210 and a material of the second semiconductor layer 220. According toone embodiment of the present application, the photoelectric conversionlayer 201 may include a material including a Group IV element, and thefirst semiconductor layer 210 may include a material including a GroupIV element. According to one embodiment of the present application, theGroup IV element of the first semiconductor layer 210 is different fromthe Group IV element of the photoelectric conversion layer 201.According to one embodiment of the present application, for example, thephotoelectric conversion layer 201 is configured to absorb photonshaving a peak wavelength in an invisible wavelength range not less than800 nm, such as 850 nm, 940 nm, 1050 nm, 1064 nm, 1310 nm, 1350 nm, or1550 nm. In some embodiments, the invisible wavelength range is not morethan 2000 nm. According to one embodiment of the present application,the photoelectric conversion layer 201 may include Ge or GeSi. Accordingto one embodiment of the present application, the photoelectricconversion layer 201 is composed of Ge or GeSi. According to oneembodiment of the present application, for example, the material of thefirst semiconductor layer 210 and the material of the secondsemiconductor layer 220 include Si.

According to one embodiment of the present application, for example, thephotoelectric conversion layer 201 may be a crystalline layer, the firstsemiconductor layer 210 may be an amorphous layer, and the secondsemiconductor layer 220 may be a crystalline layer. The material of thephotoelectric conversion layer 201 is different from both a material ofthe first semiconductor layer 210 and a material of the secondsemiconductor layer 220. A first heterojunction is formed between thephotoelectric conversion layer 201 and the first semiconductor layer210, and a second heterojunction is formed between the photoelectricconversion layer 201 and the second semiconductor layer 220. Since thefirst semiconductor layer 210 has an atomic arrangement different fromthat of the second semiconductor layer 220, the optoelectronic unit 20includes an asymmetric double heterojunction configuration.

According to one embodiment of the present application, for example, thephotoelectric conversion layer 201 may be an intrinsic crystalline Gelayer, the first semiconductor layer 210 may be an intrinsic amorphousSi layer, and the second semiconductor layer 220 may be an intrinsiccrystalline Si layer. A first heterojunction is formed between thephotoelectric conversion layer 201 and the first semiconductor layer210, and a second heterojunction is formed between the photoelectricconversion layer 201 and the second semiconductor layer 220. Since thefirst semiconductor layer 210 has an atomic arrangement different fromthat of the second semiconductor layer 220, the optoelectronic unit 20includes an asymmetric double intrinsic heterojunction configuration.

It is to be understood that in some embodiments, the amorphous Si layermay be transformed into polycrystalline Si layer or microcrystalline Silayer after a thermal process or other process treatments. According toone embodiment of the invention, the first semiconductor layer 210 andthe second semiconductor layer 220 may have different conductivitytypes, for example, the first semiconductor layer 210 may be lightly Pdoped, such as not more than 1×10¹⁷ cm⁻³, and the second semiconductorlayer 220 may be lightly N-doped, such as not more than 1×10¹⁷ cm⁻³.Further, in some embodiments, the intrinsic crystalline Ge layer may beP type without doping. In some embodiments, the photoelectric conversionlayer 201 may be lightly P doped or N doped, such as not more than1×10¹⁷ cm⁻³.

According to one embodiment of the present application, theoptoelectronic device 1 may further include a first contact layer 230disposed on an upper surface 210 a of the first semiconductor layer 210.According to one embodiment of the present application, theoptoelectronic device 1 may further include a second contact layer 240disposed on a lower surface 220 b of the second semiconductor layer 220.According to one embodiment of the present application, a conductivitytype of the second contact layer 240 is different from a conductivitytype of the first contact layer 230. For example, the first contactlayer 230 may be a P-type layer, and the second contact layer 240 may bean N-type layer. According to one embodiment of the present application,the first contact layer 230 and the second contact layer 240 includesemiconductor material. According to one embodiment of the presentapplication, the first contact layer 230 has a band gap greater than aband gap of the photoelectric conversion layer 201. According to oneembodiment of the present application, the second contact layer 240 alsohas a band gap greater than the band gap of the photoelectric conversionlayer 201. According to one embodiment of the present application, thefirst contact layer 230 has an atomic arrangement that is different fromthat of the second contact layer 240. For example, the first contactlayer 230 may be an amorphous layer, and the second contact layer 240may be a crystalline layer. According to one embodiment of the presentapplication, the atomic arrangement of the first contact layer 230 isthe same as the first semiconductor layer 210. The atomic arrangement ofthe second contact layer 240 is the same as the second semiconductorlayer 220. For example, the first contact layer 230 may be an amorphouslayer, and the first semiconductor layer 210 may also be an amorphouslayer. For another example, the second contact layer 240 may be acrystalline layer, and the second semiconductor layer 220 may also be acrystalline layer.

According to one embodiment of the present application, an opticalsignal may enter the photoelectric conversion layer 201 from the firstcontact layer 230, from the second contact layer 240 or from a side wallof the photoelectric conversion layer 201 at an angle equal or greaterthan 0 degree, wherein the side wall is between the first side 201 a andthe second side 201 b.

According to one embodiment of the present application, theoptoelectronic device 1 may further include a conductive contact element250 disposed on an upper surface 230 a of the first contact layer 230and a conductive contact element 260 disposed on a lower surface 240 bof the second contact layer 240. The conductive contact element 250includes conductive material, such as metal or transparent conductingoxides or transparent conducting films.

According to one embodiment of the present application, the firstcontact layer 230 has a peak concentration not less than 1×10¹⁸ cm⁻³,and not more than 1×10²¹ cm⁻³ for ohmically contacting with theconductive contact element 250. According to one embodiment of thepresent application, the second contact layer 240 has a peakconcentration not less than 1×10¹⁸ cm⁻³, and not more than 1×10²¹ cm⁻³for ohmically contacting with the conductive contact element 260.According to one embodiment of the present application, the secondcontact layer 240 may be formed in the substrate 10. According to oneembodiment of the present application, the first contact layer 230 has athickness not less than 10 nm, and not more than 4 μm for better backend integrability. According to one embodiment of the presentapplication, the second contact layer 240 has a thickness not less than10 nm, and not more than 4 μm for better back end integrability.

Please refer to FIG. 3. FIG. 3 is a band diagram showing the bandstructure of the optoelectronic unit 20 in FIG. 2. In FIG. 3, since theasymmetric double heterojunctions are formed in the optoelectronic unit20, a first barrier 310 and a second barrier 320 may be formed. Thefirst barrier 310 prevents the electrons from moving toward the firstsemiconductor layer 210. Similarly, the second barrier 320 prevents theholes from moving toward the second semiconductor layer 220. As aresult, the chance for the electrons to be recombined in the firstsemiconducting layer 210, the first contact layer 230, and theconducting contact element 250 is reduced; and the chance for the holesto be recombined in the second semiconducting layer 220, the secondcontact layer 240, and the conducting contact element 260 is alsoreduced. Accordingly, the V_(OC) is improved.

According to one embodiment of the present application, because thespacer layer 30 and the lens 40 are disposed to focus a larger opticalarea into a smaller optical area so that only a small optoelectronicunit 20 is needed, and therefore the photoelectric conversion layer 201in the optoelectronic unit 20 may be down-scaled. Since the width w₁ ofthe optoelectronic unit 20 is less than the width w₂ of the substrate10, the diode diffusion current at a forward-bias can be reduced, whichin turn increases V_(OC). According to one embodiment of the presentapplication, the optoelectronic device 1 is suitable for activephotovoltaic cells, and there is nearly no absorption (or very littleabsorption) in the first semiconductor layer 210 and the secondsemiconductor layer 220.

FIG. 4 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 2 in accordance with another embodiment of thepresent application, wherein similar layers, regions or elements aredesignated by the same numeral numbers. As shown in FIG. 4, theoptoelectronic device 2 includes a substrate 10, an optoelectronic unit20 supported by the substrate 10, and an optical element E disposed onan upper surface 10 a of the substrate 10. According to one embodimentof the present application, for example, the substrate 10 may includesilicon. According to one embodiment of the present application, forexample, the optical element E may include a spacer layer 30 disposed onthe optoelectronic unit 20 and the silicon substrate 10, and a lens 40disposed on the spacer layer 30.

According to one embodiment of the present application, the spacer layer30 is not in direct contact with the optoelectronic unit 20. Accordingto one embodiment of the present application, the optoelectronic device2 further includes a carrier 60 bonded to a lower surface 10 b of thesubstrate 10. A bonding layer 70 may be disposed between the lowersurface 10 b of the substrate 10 and the carrier 60. According to oneembodiment of the present application, the carrier 60 and theoptoelectronic unit 20 are connected together by the bonding layer 70.According to one embodiment of the present application, the carrier 60may include a silicon substrate, but is not limited thereto. Accordingto one embodiment of the present application, the bonding layer 70 mayinclude dielectric material, oxide material, and/or metal material, suchas Au and/or In.

FIG. 5A is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 a in accordance with still another embodimentof the present application. For example, the optoelectronic device 20 amay be a photovoltaic cell. As shown in FIG. 5A, the optoelectronicdevice 20 a includes a substrate 200, a first semiconductor region 230 pof a first conductivity type; a second semiconductor region 240 n of asecond conductivity type different from the first conductivity type; anda photoelectric conversion region 201 p between the first semiconductorregion 230 p and the second semiconductor region 240 n. In other words,the first semiconductor region 230 p and the second semiconductor region240 n with different conductivity types are at two opposite sides of thephotoelectric conversion region 201 p. The second semiconductor region240 n can be formed in the substrate 200. The photoelectric conversionregion 201 p is supported by the substrate 200. According to oneembodiment of the present application, the material of the substrate 200is different from the material of the photoelectric conversion region201 p. The photoelectric conversion region 201 p is of a thirdconductivity type the same as the first conductivity type. In someembodiments, the first conductivity type is P type, and the secondconductivity type is N type. In some embodiments, a conductive contactelement 250 such as an electrode may be disposed on the firstsemiconductor region 230 p and a conductive contact element 260 such asa electrode may be disposed on the second semiconductor region 240 n.The conductive contact elements 250, 260 include conductive materialsuch as metal or transparent conducting oxides or transparent conductingfilms. In some embodiments, the conductive contact elements 250, 260 canbe on the same side of the substrate 200.

According to some embodiments, the first semiconductor region 230 pincludes a first dopant having a first peak concentration not less than1×10¹⁸ cm⁻³. The second semiconductor region 240 n includes a seconddopant having a second peak concentration not less than 1×10¹⁸ cm⁻³. Thephotoelectric conversion region 201 p includes a third dopant having athird peak concentration. In some embodiments, the third peakconcentration is not less than 1×10¹⁷ cm⁻³. According to someembodiments, the third peak concentration is between 1×10¹⁷ cm⁻³ and1×10¹⁹ cm⁻³.

According to some embodiments, the first peak concentration is higherthan the third peak concentration. According to some embodiments, thefirst dopant and the third dopant can be a P-type dopant including agroup-III element. The first dopant and the third dopant can be the sameof can be different. In some embodiments, the P-type dopant is boron.The second dopant includes an N-type dopant. The N-type dopant can be agroup-V element. In some embodiments, the N-type dopant is phosphorous.According to some embodiments, a material of the first semiconductorregion 230 p is different from a material of the photoelectricconversion region 201 p. In some embodiment, a material of the secondsemiconductor region 240 n is different from the material of thephotoelectric conversion region 201 p.

According to some embodiments, a band gap of the first semiconductorregion 230 p is greater than a band gap of the photoelectric conversionregion 201 p. According to some embodiments, a band gap of the secondsemiconductor region 240 n is greater than a band gap of thephotoelectric conversion region 201 p.

According to some embodiments, the photoelectric conversion region 201 pincludes germanium or is composed of germanium. According to someembodiments, the photoelectric conversion region 201 p includes GeSi oris composed of GeSi. According to some embodiments, the firstsemiconductor region 230 p includes silicon or is composed of silicon.According to some embodiments, the second semiconductor region 240 nincludes silicon or is composed of silicon.

For example, the first semiconductor region 230 p may include amorphoussilicon, polycrystalline silicon or single crystalline silicon. Thefirst semiconductor region 230 p may be P-type and has a dopingconcentration not less than 1×10¹⁹ cm⁻³. For example, the secondsemiconductor region 240 n may include crystalline Si and may be N-type.The second semiconductor region 240 n has a doping concentration notless 1×10¹⁹ cm⁻³. For example, the photoelectric conversion region 201 pmay include crystalline Ge having a doping concentration ranging from1×10¹⁷ cm⁻³ to 1×10¹⁹ cm⁻³. For another example, the photoelectricconversion region 201 p may include crystalline Ge layer having a dopingconcentration not less 1×10¹⁹ cm⁻³.

FIG. 5B is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 a′ in accordance with still another embodimentof the present application. The conductive contact elements 250, 260 canbe at two opposite sides of the substrate 200. In other words, thesubstrate 200 is between the conductive contact elements 250, 260.According to some embodiments, the substrate 200 is of a conductivitytype. In some embodiments, the conductivity type is N-type. In someembodiments, the substrate 200 includes an N-type dopant having aconcentration profile including a lowest concentration. In someembodiments, the concentration profile is measured from a top surface ofthe substrate 200 to a bottom surface of the substrate 200. In someembodiments, the lowest concentration of the N-type dopant is between1×10¹² cm⁻³ and 5×10¹⁴ cm⁻³ and the thickness of the substrate 200 isnot more than 100 μm for a large open-circuit voltage (V_(OC)) and alarge short-circuit current (I_(SC)). In some embodiments, the lowestconcentration of the N-type dopant is greater than 1×10¹⁵ cm⁻³ orgreater than 1×10¹⁶ cm⁻³, and the thickness of the substrate 200 can begreater than 100 μm. In other words, by doping an N-type dopant into thesubstrate 200 with a lowest concentration greater than 1×10¹⁵ cm⁻³, thethickness of the substrate 200 can be greater than greater than 100 μm,which is beneficial for the manufacturing process of the optoelectronicdevice 20 a′, and the optoelectronic device 20 a′ can be with largeopen-circuit voltage (V_(OC)) and a large short-circuit current (I_(SC))at the same time. In some embodiments, the lowest concentration of theN-type dopant is between than 1×10¹⁶ cm⁻³ and 1×10¹⁹ cm⁻³. In someembodiments, the substrate 200 is composed of crystalline Si.

According to some embodiments, a material of the first semiconductorregion 230 p is the same as a material of the photoelectric conversionregion 201 p. In some embodiments, a material of the secondsemiconductor region 240 n is the same as the material of thephotoelectric conversion region 201 p. For example, the firstsemiconductor region 230 p, the photoelectric conversion region 201 pand the second semiconductor region 240 n all include Ge or GeSi. Foranother example, the first semiconductor region 230 p, the photoelectricconversion region 201 p and the second semiconductor region 240 n areall composed of Ge or Ge Si.

FIG. 6 is a band diagram showing the band structure of the exemplaryoptoelectronic device 20 a of FIG. 5A. It is understood that FIG. 5A isfor illustration purposes only. The band diagram does not accuratelyreflect the barriers caused by band offset or built-in potential. Byemploying intentionally doped photoelectric conversion region 201 p, abarrier can be formed between the photoelectric conversion region 201 pand the second semiconductor region 240 n. As a result, theforward-biased electrons can be prevented from drifting into thephotoelectric conversion region 201 p by the barrier between thephotoelectric conversion region 201 p and the second semiconductorregion 240 n. In other words, the forward-biased electrons and the holescan be separated by the barrier and be at the two opposite sides of theinterface between the second semiconductor region 240 n and thephotoelectric conversion region 201 p. Therefore, the Schocky-Read-Hallrecombination can be decreased, thereby increasing V_(OC). Furthermore,in some embodiments, since the band gap of the second semiconductorregion 240 n is greater than the band gap of the photoelectricconversion region 201 p and/or the band gap of the first semiconductorregion 230 p is greater than the band gap of the photoelectricconversion region 201 p, the barrier between the photoelectricconversion region 201 p and the second semiconductor region 240 n can beenlarged and thus the forward-biased electrons can be further preventedfrom drifting into the photoelectric conversion region 201 p.Accordingly, V_(OC) can be further increased.

According to some embodiments, the first dopant in the firstsemiconductor region 230 p can be an N-type dopant, the third dopant inthe photoelectric conversion region 201 p can be an N-type dopant, andthe second dopant in the second semiconductor region 240 n can be aP-type dopant. By employing intentionally doped photoelectric conversionregion 201 p, a barrier can be formed between first semiconductor region230 p and the photoelectric conversion region 201 p. As a result, theforward-biased holes can be prevented from drifting into thephotoelectric conversion region 201 p by the barrier between thephotoelectric conversion region 201 p and the first semiconductor region230 p. In other words, forward-biased holes and the electrons can beseparated by the barrier and be at the two opposite sides of theinterface between the first semiconductor region 230 p and thephotoelectric conversion region 201 p. Therefore, the Schocky-Read-Hallrecombination can be decreased, thereby increasing V_(OC). Furthermore,in some embodiments, since the band gap of the first semiconductorregion 230 p is greater than the band gap of the photoelectricconversion region 201 p and/or the band gap of the second semiconductorregion 240 n is greater than the band gap of the photoelectricconversion region 201 p, the barrier between the photoelectricconversion region 201 p and the first semiconductor region 230 p can beenlarged and thus the forward-biased holes can be further prevented fromdrifting into the photoelectric conversion region 201 p. Accordingly,V_(OC) can be further increased.

FIG. 7 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 b in accordance with still another embodimentof the present application, wherein similar layers, regions or elementsare designated by the same numeral numbers. As shown in FIG. 7, forexample, the second dopant of the second contact region 240 n maydiffuse into the photoelectric conversion region 201 p or can beintentionally doped into a part of the photoelectric conversion region201 p. In other words, the part of the photoelectric conversion region201 p near the second semiconductor region 240 n may include both thesecond dopant and the third dopant.

FIG. 8 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 c in accordance with still another embodimentof the present application, wherein similar layers, regions or elementsare designated by the same numeral numbers. As shown in FIG. 8, forexample, the first dopant of the first semiconductor region 230 p maydiffuse into the photoelectric conversion region 201 p.

FIG. 9 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 d in accordance with still another embodimentof the present application, wherein similar layers, regions or elementsare designated by the same numeral numbers. According to one embodiment,a material of the first semiconductor region 230 p is the same as amaterial of the photoelectric conversion region 201 p. For example, thefirst semiconductor region 230 p and the photoelectric conversion region201 p both include crystalline Ge. The second semiconductor region 240 nis located in the substrate 200 and includes crystalline Si.

FIG. 10 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 e in accordance with still another embodimentof the present application, wherein similar layers, regions or elementsare designated by the same numeral numbers. According to one embodiment,a material of the second semiconductor region 240 n is the same as thematerial of the photoelectric conversion region 201 p. For example, thefirst semiconductor region 230 p includes amorphous Si, poly crystallineSi, or crystalline Si. The photoelectric conversion region 201 p and thesecond semiconductor region 240 n both include crystalline Ge.

According to some embodiments, the optoelectronic device may furtherinclude a third semiconductor region between the photoelectricconversion region and the second semiconductor region. In someembodiments, the third semiconductor region is crystalline. In someembodiments, the third semiconductor region is for improving the qualityof the photoelectric conversion region formed thereon.

FIG. 11 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 f in accordance with still another embodimentof the present application, wherein similar layers, regions or elementsare designated by the same numeral numbers. As shown in FIG. 11, theoptoelectronic device 20 f includes a third semiconductor region 240 ibetween the photoelectric conversion region 201 p and the secondsemiconductor region 240 n. In some embodiments, the third semiconductorregion 240 i is crystalline for improving the quality of thephotoelectric conversion region 201 p formed thereon. In someembodiments, the third semiconductor region 240 i is intrinsic and has athickness not more than 200 nm for increasing the V_(OC) of theoptoelectronic device 20 f. In some embodiments, the third semiconductorregion 240 i may be of a conductivity type the same as the secondconductivity type of the second semiconductor region 240 n. In someembodiments, the third semiconductor region 240 i may includecrystalline Si. In some embodiments, the material of the thirdsemiconductor region 240 i is the same as the material of the substrate200. In some embodiments, a substantially invisible interface may bebetween the third semiconductor region 240 i and the substrate 200.

FIG. 12 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 g in accordance with still another embodimentof the present application, wherein similar layers, regions or elementsare designated by the same numeral numbers. As shown in FIG. 12, theoptoelectronic device 20 g includes a fourth semiconductor region 201 ibetween the photoelectric conversion region 201 p and the secondsemiconductor region 240 n. The fourth semiconductor region 201 i isintrinsic. The fourth semiconductor region 201 i may be an undoped orlightly doped region, such as having a peak concentration not more than1×10¹⁶ cm⁻³. According to one embodiment, the fourth semiconductorregion 201 i may include crystalline Ge, which can ease the epitaxygrowth of the photoelectric conversion region 201 p. According to someembodiments, an optoelectronic device can also include both a thirdsemiconductor region 240 i (as set forth in FIG. 11) and a fourthsemiconductor region 201 i, wherein the third semiconductor region 240 iis between the second semiconductor region 240 n and the photoelectricconversion region 201 p, and the fourth semiconductor region 201 i isbetween the third semiconductor region 240 i and the photoelectricconversion region 201 p.

According to some embodiments, the third dopant of the photoelectricconversion region may have a concentration, wherein the concentration isgraded along a direction from the first semiconductor region with theconductivity type the same as the conductivity type of the photoelectricconversion region to the second semiconductor region with theconductivity type the different from the conductivity type of thephotoelectric conversion region. In some embodiments, the concentrationis gradually decreased along a direction from the first semiconductorregion to the second semiconductor region. According to someembodiments, the concentration is gradually decreased along a directionfrom the P-type first semiconductor region to the N-type secondsemiconductor region when the photoelectric conversion region is P-type.

FIG. 13 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 h in accordance with still another embodimentof the present application, wherein similar layers, regions or elementsare designated by the same numeral numbers. As shown in FIG. 13, thephotoelectric conversion region 201 p includes the third dopant (e.g., Ptype dopant) having a concentration, wherein the concentration is gradedalong a direction D₁ from the first semiconductor region 230 p to thesecond semiconductor region 240 n. In some embodiments, theconcentration is gradually decreased along the direction D₁ from thefirst semiconductor region 230 p to the second semiconductor region 240n.

According to some embodiments, an optoelectronic device may include aphotoelectric conversion region including a first side and a second sideopposite to the first side; a first semiconductor region of a firstconductivity type; and a second semiconductor region of a secondconductivity type different from the first conductivity type. The firstsemiconductor region and the second semiconductor region are both overthe first side of photoelectric conversion region. The photoelectricconversion region is of a third conductivity type the same as the firstconductivity type.

In some embodiments, the optoelectronic device further includes a thirdsemiconductor region separating the photoelectric conversion region andthe second semiconductor region. In some embodiments, the thirdsemiconductor region is similar with that as described in FIG. 11.

In some embodiments, the first semiconductor region is in direct contactwith the photoelectric conversion region. In some embodiments, the firstsemiconductor region serves as a semiconductor contact region. In someembodiments, the second semiconductor region is in direct contact withthe photoelectric conversion region. In some embodiments, the secondsemiconductor region serves as a semiconductor contact region.

In some embodiments, a material of the first semiconductor region isdifferent from a material of the photoelectric conversion region. Insome embodiments, the material of the first semiconductor region is thesame as a material of the second semiconductor region. In someembodiments, a direction from the first semiconductor region to thesecond semiconductor region is substantially perpendicular to adirection from the first side and the second side of the photoelectricconversion region. In some embodiments, the first semiconductor regionis physically separated from the second semiconductor region.

FIG. 14A is a schematic, top-view diagram showing an exemplaryoptoelectronic device 20 i in accordance with still another embodimentof the present application. FIG. 14B is a schematic, cross-sectionaldiagram along an A-A′ line in FIG. 14A, wherein similar layers, regionsor elements are designated by the same numeral numbers. Thephotoelectric conversion region 201 p includes a first side 201 a and asecond side 201 b opposite to the first side 201 a. A firstsemiconductor region 230 p of a first conductivity type (e.g., P type)is disposed in the substrate 200. In some embodiments, the firstsemiconductor region 230 p includes crystalline Si. A secondsemiconductor region 240 n of a second conductivity type (e.g., N type)different from the first conductivity type is also disposed in thesubstrate 200. In some embodiments, the second semiconductor region 240n includes crystalline Si. The first semiconductor region 230 p and thesecond semiconductor region 240 n are both disposed on the first side201 a of photoelectric conversion region 201 p. The photoelectricconversion region 201 p is of a third conductivity type the same as thefirst conductivity type.

In some embodiments, the optoelectronic device 20 i further includes apassivation layer 240 covering a top surface of the photoelectricconversion region 201 p. In some embodiments, the passivation layer 240covers the top surface of the photoelectric conversion region 201 p andcovers all the side walls of the photoelectric conversion region 201 p.In some embodiment, a material of the passivation layer 240 is differentfrom a material of the photoelectric conversion region 201 p. In someembodiments, the passivation layer 240 reduces surface defects of thephotoelectric conversion region 201 p. In some embodiments, thepassivation layer 240 protects the surface of the photoelectricconversion region 201 p from contamination or damages from theenvironment. In some embodiments, the passivation layer 240 includesamorphous silicon.

As shown in FIG. 14A and FIG. 14B, the first semiconductor region 230 pand the second semiconductor region 240 n are formed at a side of thesubstrate near the photoelectric conversion region 201 p. The firstsemiconductor region 230 p includes a first main portion 231 p. Thesecond semiconductor region 240 n includes a second main portion 241 n.The first main portion 231 p and the second main portion 241 n aredisposed at two opposite sides of the photoelectric conversion region201 p and are not covered by the photoelectric conversion region 201 p.The first semiconductor region 230 p further includes a first extensionportion 232 p extending from the first main portion 231 p toward thesecond main portion 241 n. The second semiconductor region 240 n furtherincludes a second extension portion 242 n extending from the second mainportion 241 n toward the first main portion 231 p. The first extensionportion 232 p and the second extension portion 242 n are covered by thephotoelectric conversion region 201 p. The conductive contact element250 is disposed on the first main portion 231 p. The conductive contactelement 260 is disposed on the second main portion 241 n. In someembodiments, the first semiconductor region 230 p includes multiplefirst extension portions 232 p each extending from the first mainportion 231 p toward the second main portion 241 n and separated fromeach other. In some embodiments, the second semiconductor region 240 nfurther includes multiple second extension portions 242 n each extendingfrom the second main portion 241 n toward the first main portion 231 pand separated from each other. The multiple first extension portions 232p and the multiple second extension portions 242 n are arrangedalternately and are covered by the photoelectric conversion region 201p.

According to one embodiment, the first semiconductor region 230 p isphysically separated from the second semiconductor region 240 n. Theoptoelectronic device 20 i further includes a third semiconductor region240 i separating the photoelectric conversion region 201 p and the firstsemiconductor region 230 p and separating the photoelectric conversionregion 201 p and the second semiconductor region 240 n. In other words,the third semiconductor region 240 i is between the photoelectricconversion region 201 p and the first semiconductor region 230 p. Thethird semiconductor region 240 i is between the photoelectric conversionregion 201 p and the second semiconductor region 240 n. In someembodiments, the third semiconductor region 240 i is intrinsic. In someembodiments, the conductive contact element 250 such as electrode is indirect contact with the first semiconductor region 230 p. In otherwords, the first semiconductor region 230 p serves as a semiconductorcontact region. In some embodiments, the conductive contact element 260such as electrode is in direct contact with the second semiconductorregion 240 n. In other words, the second semiconductor region 240 nserves as a semiconductor contact region.

A material of the first semiconductor region 230 p is different from amaterial of the photoelectric conversion region 201 p. In someembodiments, the material of the first semiconductor region 230 p is thesame as a material of the second semiconductor region 240 n. A directionfrom the first semiconductor region 230 p to the second semiconductorregion 240 n is substantially perpendicular to a direction from thefirst side 201 a to the second side 201 b of the photoelectricconversion region 201 p.

FIG. 15 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 j in accordance with still another embodimentof the present application, wherein the optoelectronic device 20 j has atop view similar to the top view in FIG. 14A and the cross-sectionaldiagram is along an B-B′ line in FIG. 14A, and wherein similar layers,regions or elements are designated by the same numeral numbers. As shownin FIG. 15, the optoelectronic device 20 j includes a photoelectricconversion region 201 p including a first side 201 a and a second side201 b opposite to the first side 201 a. A first semiconductor region 230p of a first conductivity type (e.g., P type) is disposed in thesubstrate 200. A second semiconductor region 240 n of a secondconductivity type (e.g., N type) different from the first conductivitytype is disposed in the substrate 200 and separated from the firstsemiconductor region 230 p. The first semiconductor region 230 p and thesecond semiconductor region 240 n are both disposed on the first side201 a of photoelectric conversion region 201 p. The photoelectricconversion region 201 p is of a third conductivity type the same as thefirst conductivity type.

According to one embodiment, the optoelectronic device 20 j furtherincludes a third semiconductor region 240 i separating the photoelectricconversion region 201 p from the second semiconductor region 240 n andseparating the first semiconductor region 230 p from the photoelectricconversion region 201 p. In other words, the third semiconductor region240 i is between the photoelectric conversion region 201 p and the firstsemiconductor region 230 p. The third semiconductor region 240 i isbetween the photoelectric conversion region 201 p and the secondsemiconductor region 240 n. In some embodiments, the third semiconductorregion 240 i is intrinsic. In some embodiments, the first dopant of thefirst semiconductor region 230 p may diffuse into the thirdsemiconductor region 240 i during the manufacturing process of theoptoelectronic device, such as the step of forming the thirdsemiconductor region 240 i. As a result, a part 240 ia of the thirdsemiconductor region 240 i between the first semiconductor region 230 pand the photoelectric conversion region 201 p includes the first dopant.

The conductive contact element 250 such as electrode is in directcontact with the first semiconductor region 230 p. In other words, thefirst semiconductor region 230 p serves as a semiconductor contactregion. The conductive contact element 260 such as electrode is indirect contact with the second semiconductor region 240 n. In otherwords, the second semiconductor region 240 n serves as a semiconductorcontact region.

According to one embodiment, the first semiconductor region 230 p isphysically separated from the second semiconductor region 240 n.According to one embodiment, the optoelectronic device 20 j furtherincludes a fourth semiconductor region between the third semiconductorregion 240 i and the photoelectric conversion region 201 p. The fourthsemiconductor region can be similar to the fourth semiconductor region201 i as described in FIG. 12.

A material of the first semiconductor region 230 p is different from amaterial of the photoelectric conversion region 201 p. In someembodiments, the material of the first semiconductor region 230 p is thesame as a material of the second semiconductor region 240 n. A directionfrom the first semiconductor region 230 p to the second semiconductorregion 240 n is substantially perpendicular to a direction from thefirst side 201 a to the second side 201 b of the photoelectricconversion region 201 p.

FIG. 16 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 k in accordance with still another embodimentof the present application, wherein the optoelectronic device 20 k has atop view similar to the top view in FIG. 14A and the cross-sectionaldiagram is along an A-A′ line in FIG. 14A, and wherein similar layers,regions or elements are designated by the same numeral numbers. As shownin FIG. 16, the optoelectronic device 20 k includes a photoelectricconversion region 201 p including a first side 201 a and a second side201 b opposite to the first side 201 a. A first semiconductor region 230p of a first conductivity type (e.g., P type) is disposed in thesubstrate 200. A second semiconductor region 240 n of a secondconductivity type (e.g., N type) different from the first conductivitytype is disposed in the substrate 200 and physically separated from thefirst semiconductor region 230 p. The first semiconductor region 230 pand the second semiconductor region 240 n are both disposed on the firstside 201 a of photoelectric conversion region 201 p. The photoelectricconversion region 201 p is of a third conductivity type the same as thefirst conductivity type.

According to one embodiment, the optoelectronic device 20 k furtherincludes a third semiconductor region 240 i separating the photoelectricconversion region 201 p from the first semiconductor region 230 p andseparating the photoelectric conversion region 201 p from the secondsemiconductor region 240 n. In some embodiments, the third semiconductorregion 240 i is intrinsic.

In some embodiments, the second dopant of the second semiconductorregion 240 n may diffuse into the third semiconductor region 240 iduring the manufacturing process of the optoelectronic device, such asthe step of forming the third semiconductor region 240 i. As a result, apart 240 ib of the third semiconductor region 240 i between the secondsemiconductor region 240 n and the photoelectric conversion region 201 pincludes the second dopant.

The conductive contact element 250 such as electrode is in directcontact with the first semiconductor region 230 p. In other words, thefirst semiconductor region 230 p serves as a semiconductor contactregion. The conductive contact element 260 such as electrode is indirect contact with the second semiconductor region 240 n. In otherwords, the second semiconductor region 240 n serves as a semiconductorcontact region.

According to one embodiment, the first semiconductor region 230 p isphysically separated from the second semiconductor region 240 n.According to one embodiment, the optoelectronic device 20 k furtherincludes a fourth semiconductor region between the third semiconductorregion 240 i and the photoelectric conversion region 201 p. The fourthsemiconductor region can be similar to the fourth semiconductor region201 i as described in FIG. 12.

A material of the first semiconductor region 230 p is different from amaterial of the photoelectric conversion region 201 p. In someembodiments, the material of the first semiconductor region 230 p is thesame as a material of the second semiconductor region 240 n. A directionfrom the first semiconductor region 230 p to the second semiconductorregion 240 n is substantially perpendicular to a direction from thefirst side 201 a to the second side 201 b of the photoelectricconversion region 201 p.

FIG. 17 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 201 in accordance with still another embodiment ofthe present application, wherein the optoelectronic device 201 has a topview similar to the top view in FIG. 14A and the cross-sectional diagramis along an C-C′ line in FIG. 14A, and wherein similar layers, regionsor elements are designated by the same numeral numbers. As shown in FIG.17, the optoelectronic device 201 includes a photoelectric conversionregion 201 p including a first side 201 a and a second side 201 bopposite to the first side 201 a. A first semiconductor region 230 p ofa first conductivity type (e.g., P type) is disposed in the substrate200. A second semiconductor region 240 n of a second conductivity type(e.g., N type) different from the first conductivity type is disposed inthe substrate 200 and physically separated from the first semiconductorregion 230 p. The first semiconductor region 230 p and the secondsemiconductor region 240 n are both disposed on the first side 201 a ofphotoelectric conversion region 201 p. The photoelectric conversionregion 201 p is of a third conductivity type the same as the firstconductivity type.

According to one embodiment, the first semiconductor region 230 p isphysically separated from the second semiconductor region 240 n. Theoptoelectronic device 201 further includes a third semiconductor region240 i separating the first semiconductor region 230 p from the secondsemiconductor region 240 n. In some embodiments, the third semiconductorregion 240 i is intrinsic.

In some embodiments, the first dopant of the first semiconductor region230 p may diffuse into the third semiconductor region 240 i during themanufacturing process of the optoelectronic device, such as the step offorming the third semiconductor region 240 i. As a result, a part 240 iaof the third semiconductor region 240 i between the first semiconductorregion 230 p and the photoelectric conversion region 201 p includes thefirst dopant. In some embodiments, the second dopant of the secondsemiconductor region 240 n may diffuse into the third semiconductorregion 240 i during the manufacturing process of the optoelectronicdevice, such as the step of forming the third semiconductor region 240i. As a result, a part 240 ib of the third semiconductor region 240 ibetween the second semiconductor region 240 n and the photoelectricconversion region 201 p includes the second dopant. In other words, thethird semiconductor region 240 i may include both the first dopant andthe second dopant.

The conductive contact element 250 such as electrode is in directcontact with the first semiconductor region 230 p. In other words, thefirst semiconductor region 230 p serves as a semiconductor contactregion. The conductive contact element 260 such as electrode is indirect contact with the second semiconductor region 240 n. In otherwords, the second semiconductor region 240 n serves as a semiconductorcontact region.

A material of the first semiconductor region 230 p is different from amaterial of the photoelectric conversion region 201 p. In someembodiments, the material of the first semiconductor region 230 p is thesame as a material of the second semiconductor region 240 n. A directionfrom the first semiconductor region 230 p to the second semiconductorregion 240 n is substantially perpendicular to a direction from thefirst side 201 a to the second side 201 b of the photoelectricconversion region 201 p.

FIG. 18 is a schematic, cross-sectional diagram showing an exemplaryoptoelectronic device 20 m in accordance with still another embodimentof the present application, wherein the optoelectronic device 20 m has atop view similar to the top view in FIG. 14A and the cross-sectionaldiagram is along an A-A′ line in FIG. 14A, and wherein similar layers,regions or elements are designated by the same numeral numbers. As shownin FIG. 18, the optoelectronic device 20 m includes a photoelectricconversion region 201 p including a first side 201 a and a second side201 b opposite to the first side 201 a. A first semiconductor region 230p of a first conductivity type (e.g., P type) is disposed in thesubstrate 200. A second semiconductor region 240 n of a secondconductivity type (e.g., N type) different from the first conductivitytype is disposed in the substrate 200 and physically separated from thefirst semiconductor region 230 p. The first semiconductor region 230 pand the second semiconductor region 240 n are both disposed on the firstside 201 a of photoelectric conversion region 201 p. The photoelectricconversion region 201 p is of a third conductivity type the same as thefirst conductivity type.

According to one embodiment, the first semiconductor region 230 p isphysically separated from the second semiconductor region 240 n. Theoptoelectronic device 20 m further includes a third semiconductor region240 i separating the photoelectric conversion region 201 p, the firstsemiconductor region 230 p and the second semiconductor region 240 n. Insome embodiments, the third semiconductor region 240 i is intrinsic. Theconductive contact element 250 such as electrode is in direct contactwith the first semiconductor region 230 p. In other words, the firstsemiconductor region 230 p serves as a semiconductor contact region. Theconductive contact element 260 such as electrode is in direct contactwith the second semiconductor region 240 n. In other words, the secondsemiconductor region 240 n serves as a semiconductor contact region.

A material of the first semiconductor region 230 p is different from amaterial of the photoelectric conversion region 201 p. In someembodiments, the material of the first semiconductor region 230 p is thesame as a material of the second semiconductor region 240 n. A directionfrom the first semiconductor region 230 p to the second semiconductorregion 240 n is substantially perpendicular to a direction from thefirst side 201 a to the second side 201 b of the photoelectricconversion region 201 p.

According to one embodiment, the photoelectric conversion region 201 pincludes a dopant (e.g., P type dopant) having a concentration, whereinthe concentration is graded along a direction D₂ from the firstsemiconductor region 230 p to the second semiconductor region 240 n. Insome embodiments, the concentration is gradually decreased along thedirection D₂ from the first semiconductor region 230 p with theconductivity type the same as the conductivity type of the photoelectricconversion region 201 p to the second semiconductor region 240 n withthe conductivity type the different from the conductivity type of thephotoelectric conversion region 201 p to facilitate electron transport.According to some embodiments, the concentration is gradually decreasedalong a direction from the p-type first semiconductor region 230 p tothe N-type second semiconductor region 240 n when the photoelectricconversion region 201 p is P-type.

In some embodiments, the structure of the optoelectronic device or thephotovoltaic cell may be a combination of the previously shownembodiments. It is to be understood that the conductivity types of thelayers can be opposite. For example, in some embodiment, the P⁺ regioncan be N⁺ region, the N⁺⁺ region can be P⁺⁺ region, and the P⁺⁺ regioncan be N⁺⁺ region.

FIG. 19 demonstrates simulation results of I-V curves of optoelectronicdevices in FIG. 11 with different peak concentrations of the dopant inthe photoelectric conversion region 201 p, wherein the photoelectricconversion region 201 p is composed of germanium. In FIG. 19, theoptoelectronic devices with a photoelectric conversion region 201 phaving a peak concentration between 1×10¹⁷ cm⁻³ and 1×10¹⁹ cm⁻³ haverelatively better Voc.

Please refer to FIG. 20, which shows the I-V curves of differentoptoelectronic devices with the photoelectric conversion region 201 pcomposed of germanium and having a peak concentration about 1×10¹⁸ cm⁻³.As shown in FIG. 20, each of the optoelectronic devices in accordancewith the present application has good Voc.

According to one embodiment, the optoelectronic device may be aphotodetector.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An optoelectronic device, comprising: a firstsemiconductor region of a first conductivity type; a secondsemiconductor region of a second conductivity type different from thefirst conductivity type; and a photoelectric conversion region betweenthe first semiconductor region and the second semiconductor region,wherein the photoelectric conversion region is of a third conductivitytype the same as the first conductivity type.
 2. The optoelectronicdevice according to claim 1, wherein the first semiconductor regioncomprises a first dopant having a first peak concentration, the secondsemiconductor region comprises a second dopant having a second peakconcentration, the photoelectric conversion region comprises a thirddopant having a third peak concentration, and wherein the third peakconcentration is not less than 1×10¹⁷ cm⁻³.
 3. The optoelectronic deviceaccording to claim 2, wherein the first peak concentration is higherthan the third peak concentration.
 4. The optoelectronic deviceaccording to claim 1, wherein a material of the first semiconductorregion is the same as a material of the photoelectric conversion region,and wherein a material of the second semiconductor region is the same asthe material of the photoelectric conversion region.
 5. Theoptoelectronic device according to claim 1, wherein a material of thefirst semiconductor region is different from a material of thephotoelectric conversion region, and wherein a material of the secondsemiconductor region is different from the material of the photoelectricconversion region.
 6. The optoelectronic device according to claim 1,wherein the photoelectric conversion region comprises germanium.
 7. Theoptoelectronic device according to claim 1, wherein the firstsemiconductor region comprises a band gap greater than a band gap of thephotoelectric conversion layer.
 8. The optoelectronic device accordingto claim 1, wherein the second semiconductor region comprises siliconand/or the first semiconductor region comprises silicon.
 9. Theoptoelectronic device according to claim 1, wherein the photoelectricconversion region comprises a dopant having a concentration, wherein theconcentration is graded along a direction from the first semiconductorregion to the second semiconductor region.
 10. The optoelectronic deviceaccording to claim 9, wherein the concentration is gradually decreasedalong a direction from the first semiconductor region to the secondsemiconductor region.
 11. The optoelectronic device according to claim1, wherein the first conductivity type is P type and the secondconductivity type is N type.
 12. The optoelectronic device according toclaim 1, further comprising a third semiconductor region between thephotoelectric conversion region and the second semiconductor region. 13.The optoelectronic device according to claim 2, wherein thephotoelectric conversion region comprises both the second dopant and thethird dopant.
 14. An optoelectronic device, comprising: a photoelectricconversion region comprising a first side and a second side opposite tothe first side; a first semiconductor region of a first conductivitytype; and a second semiconductor region of a second conductivity typedifferent from the first conductivity type; wherein the firstsemiconductor region and the second semiconductor region are both overthe first side of photoelectric conversion region, and the photoelectricconversion region is of a third conductivity type the same as the firstconductivity type.
 15. The optoelectronic device according to claim 14,wherein the photoelectric conversion region has a peak concentration notless than 1×10¹⁷ cm⁻³.
 16. The optoelectronic device according to claim14, further comprising a passivation layer covering the photoelectricconversion region.
 17. The optoelectronic device according to claim 14,wherein a material of the first semiconductor region is different from amaterial of the photoelectric conversion region, and wherein thematerial of the first semiconductor region is the same as a material ofthe second semiconductor region.
 18. The optoelectronic device accordingto claim 14, wherein a direction from the first semiconductor region tothe second semiconductor region is substantially perpendicular to adirection from the first side to the second side of the photoelectricconversion region.
 19. The optoelectronic device according to claim 14,wherein the first semiconductor region is physically separated from thesecond semiconductor region.
 20. The optoelectronic device according toclaim 14, further comprising a third semiconductor region between thephotoelectric conversion region and the first semiconductor region.